YOU SAID:

While he was doing his work he had a excellent idea

INTO JAPANESE

彼は仕事をしているときに素晴らしいアイデアを思いついた

BACK INTO ENGLISH

he came up with a brilliant idea while he was working

INTO JAPANESE

彼は仕事中に素晴らしいアイデアを思いついた

BACK INTO ENGLISH

he came up with a brilliant idea at work

INTO JAPANESE

彼は仕事中に素晴らしいアイデアを思いついた

BACK INTO ENGLISH

he came up with a brilliant idea at work